This invention relates to a shovel dipper bail assembly and, more particularly, to an assembly which permits the dipper to be raised higher on a given machine before it interferes with the boom tip sheaves than prior assemblies.
Power shovels have been employed in excavating since before the turn of the century, viz., steam shovels. Over all of these years, it is apparent that many design improvements have been made but a long-standing problem has resided in the inability of raising the dippper to the maximum height possible.
Conventionally, a power shovel includes a lifiting boom mounted on the prime mover and, intermediate the length of the boom, the dipper stick is pivotally mounted thereon. The outer end of the boom is equipped with cable sheaves and cables are entrained therein for connection with the bail of the dipper. The cables are connected to the bail of the dipper by means of a hitch assembly which heretofore has limited the height to which the dipper can be elevated. For example, in co-owned, expired U.S. Pat. No. 2,034,854, a lifting hitch is seen that projects substantially above the bight of the U-shaped bail. Such an arrangement has been generally employed down to the present where padlock lugs have been welded to the bail bight in order to provide a pivotal mounting for the hitch.
Over the years, other expedients have been attempted to increase the ability to elevate the dipper. It will be appreciated that the higher the dipper can be raised--relative to the lifting boom--the higher the bank in which the machine can be operated and it is also possible to dump from higher heights to suit larger trucks--thereby extending the performance capability range of a given machine. One expedient has consisted of "D-rings" which permitted the cable connection to the bail to be substantially at the bight level, but this expedient was rejected by the excavating art because it resulted in accelerated wear on the lifting cables.
According to the instant invention, we have achieved the goal of substantially maximum elevatability without the attendant disadvantages of the previously employed D-ring construction by utilizing a lift hitch assembly which is rotatably mounted on a cylindrical section of the bail bight. Advantageously, the cable connections are in the form of the well-known D-rings so as to provide a profile of lifting hitch which is just slightly above the bail--thereby enabling the dipper to be raised to maximum possible elevation. Even though the art workers knew of the D-ring connnections for lifting cables, and also had central cylindrical sections on the bail bights, no one was able to bring these two concepts together to provide the advantage of maximum elevatability of the dipper.
Other objects and advantages of the invention may be seen in the details of the ensuing specification.